1. Field of the Invention
The present invention relates generally to on-line printing apparatus and more particularly to a character generating system for generating characters of a nine-row-by-nine-column dot matrix format.
2. Description of the Prior Art
High-speed line printers are well known in the art, and there are continuous efforts to develop printers to accommodate the high output rate of information which can be delivered by a high-speed data processing systems. Also, print heads which can accommodate high-speed electronics are known in the prior art. For example, printers employing wire matrix ballistic impact print heads capable of providing print characters by an array of dots in rows and columns is well known. For example, such a head is shown and described in U.S. Pat. No. 3,929,214. In order to actuate the print heads utilizing a dot matrix print pattern, it is necessary to have a character generator capable of generating pulse signals representative of the dot pattern of the character to be printed. Such character generators incorporate read only memories. Heretofore, in utilizing a standard read only memory having rows of one byte (eight bits) wide places limitations on the number of dots that can be incorporated for a given character. At the same time, however, by limiting the number of dots limits the resolution of the printed character.
It has been found preferable that the fonts for a dot-printed character be in nine-by-nine dot matrix. That is, the print characters be generated by a combination of dots selected from a rectangular pattern of nine dots per row and nine dots per column. However, this has presented difficulty in view of the fact that memories of rows of one byte have a maximum of only eight bits per row, thus placing a limitation as to the number of available dots in the printing of any given character.